This invention is related to an improvement of the known method of reactive sputtering.
In the field of depositing or growing a thin film on the surface of a material to be treated such as a semiconductor substrate, the methods of chemical vapour deposition and physical vapour deposition have generally been practiced. The sputtering can be understood to belong to the method of physical vapour deposition.
However, the reactive sputtering for growing a film on the semiconductor substrate is a method in which a synergetic effect of the chemical and physical vapour depositions is achieved. In contrast to the chemical vapour depositions method, the temperature under which the film is deposited is relatively low in the reactive sputtering method, and the adhesive characterictic of the film is substantially enhanced. Thus, the method of reactive sputtering is effective to form an insulating film to cover the semiconductor devices or to insulate interconnecting layers already fabricated on a semiconductor substrate.
Particularly, in the reactive sputtering method which uses a magnetron sputtering apparatus, crossed (at right angles) electric and magnetic fields are created near a target material to enhance the efficiency in generating plasma for activating the reactive gas. And thus, with a relatively low degree of vacuum, atoms ejected by sputtering and a reactive gas are caused to react efficiently with each other. Because of this, the reactive sputtering method excells in forming a quality film having a high degree of adhesiveness, and has come to be frequently used.
In spite of these advantages found with the magnetron sputtering apparatus, it is extremely difficult to form at a high rate of growth a film which is stable both chemically and electrically.